Method and device for measuring the progress of a moving person

ABSTRACT

Embodiments of the invention provide a method and a device for measuring the progress of a moving person. The method calculating at least one of the following quantities describing the progress of the moving person: speed, step rate, step count, step length, distance and way of progress, based on values of a vertical acceleration of a body of the moving person measured by an acceleration sensor over a measured time.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/000,998, which was filed on Dec. 19, 2007. The subjectmatter of the earlier filed application is hereby incorporated byreference.

BACKGROUND

1. Field

The invention relates to measuring devices for use in physicalmeasuring, and more specifically to a method and a device for measuringthe progress of a moving person. The invention aims at providing asolution, better and simpler than prior ones, for measuring the progressof a moving person, which solution is applicable for use in a multitudeof measuring solutions for different types of locomotion.

2. Description of Related Art

In performing navigation based on inertia sensors, e.g. acceleration orangular velocity sensors, (inertia navigation), if the sensor signal isbeing integrated, it is important that the integration time is notextended too much, thus excessively increasing the error in position ordirection caused by measuring errors of the sensor. In order to preventthat, the aim often is to divide the motion into periodically repetitivecycles of sufficient brevity. The method is called step-by-stepnavigation. In athletics coaching and competitions and in fitnessexercise and other outdoor activities, such step-by-step navigation isimportant, wherein e.g. the speed of locomotion, the distance covered,the direction, the step rate (cadence), and the step time, as well asthe step length are being measured. The way of locomotion could be e.g.running, walking, pole walking, competitive walking, cross-countryskiing, downhill sports, roller skiing, skating or the like, where acyclic motion is present.

Inertia navigation can work independently, or it can be used incombination with satellite navigation, in order to improve the accuracyof satellite navigation, particularly in areas of poor coverage of thesatellite signal, for diagnostic purposes in satellite positioning errorsituations, or in order to reduce the power consumption of satellitenavigation by means of increasing the intervals between instances ofreception of the satellite signal.

In prior art, several solutions exist aiming at measuring the distancecovered by using an acceleration sensor. In inertia navigation, forexample, an acceleration sensor is most often used for measuring thedistance covered. By means of the acceleration sensor, the contact timefor the foot, i.e. the time during which the foot touches the ground,can be measured. For instance, the U.S. Pat. No. 4,578,769 disclosessuch a solution according to prior art. The method described in saidPatent Publication provides good results for high running speeds, but itis not robust for slow running, nor for walking, where the event of thefoot leaving the ground is hard to detect.

The acceleration sensor can be a simple switch or the like, which simplycounts the number of steps and estimates the distance based on thenumber of steps, and the speed based on the cadence. These devices arecalled pedometers.

As a solution in a slightly more advanced system according to prior art,the actual motion of the walker can be measured at the foot by means ofan acceleration sensor. Such solutions according to prior art aredisclosed in e.g. the US Patent Application US 2002/0040601, the U.S.Pat. No. 5,955,667 and in the Canadian Patent Publication CA 2,218,242.

In the aforementioned patent publications, measuring signals from amultitude of acceleration sensors and angular motion sensors arecombined, and significantly improved precision is achieved compared tothe one for pedometers or contact time measurements. In these solutionsaccording to prior art, the drawbacks, however, are the required numberof sensors, a linear acceleration sensor as well as an angular motionsensor, for compensating the error caused by the earth's gravitationalforce, through the inclination and its variation, as well as thecomplexity of the algorithm, which manifest themselves in the size ofthe system, its costs, and power consumption.

In order to simplify the measuring system described above, a solutionaccording to prior art has been disclosed, for using an accelerationsensor in such a way, that knowledge of the period of time the footstays immobile, as it is on the ground, is being utilized and thus, theaim has been to improve the precision through automatic resetting. Asolution according to prior art with such a technique is disclosed ine.g. U.S. Pat. No. 6,356,856. The method described in said PatentPublication suffers, however, from inaccuracy, when the inclinationchanges during the motion. Computing is complex in this case as well,and it requires power and program storage capacity.

One solution according to prior art, for detecting motion and formeasuring the duration of movement is a disclosed method based on anacceleration sensor. Such a prior art solution is disclosed, forexample, in the U.S. Pat. No. 6,298,314.

One further solution according to prior art, for a general device formeasuring the movement of an athlete is disclosed, for example, in U.S.Pat. No. 7,092,846 and in the International Patent ApplicationPublication WO 00/20874.

In literature, several solutions according to prior art, forstep-by-step navigation have been disclosed. In all these knownsolutions, combining simplicity, and thereby low cost, small size, lowpower consumption and accuracy, is a problem. The major error sourcesfor the presented solutions are the coupling of gravitation to themeasuring signal as the angle changes, unambiguous detection of thecontact between foot and ground, and foot slipping at ground contact,whereby the acceleration signal and the speed signal are distorted.

SUMMARY

The object of the invention is an improved method and device formeasuring the progress of a moving person. By means of the method anddevice according to this invention, a precision is achieved equalingthat of the best methods presented above, but with an implementationsolution of significantly reduced complexity, using one accelerationsensor without any inclination compensation. The sensor solutionaccording to the invention is applicable for use in a multitude ofsolutions for measuring different types of locomotion.

According to an embodiment of the invention, there is provided a methodfor measuring the progress of a moving person. The method includescalculating at least one of the following quantities describing theprogress of the moving person: speed, step rate, step count, steplength, distance and way of progress, based on values of a verticalacceleration of a body of the moving person measured by an accelerationsensor over a measured time.

According to another embodiment of the invention, the method furtherincludes defining step cycle-specific characteristic maximumacceleration values a_(max) falling within a positive half-cycle, duringan acceleration stage, and correspondingly step cycle-specificcharacteristic minimum acceleration values a_(min) falling within anegative half-cycle during a braking stage, based on measured values ofthe vertical acceleration of the body of the moving person.

According to another embodiment of the invention, the method furtherincludes defining the step cycle-specific characteristic maximumacceleration values a_(max) as maxima of step cycle-specific measuredacceleration values, and the step cycle-specific characteristic minimumacceleration values a_(min) as minima of the step cycle-specificmeasured acceleration values.

According to another embodiment of the invention, the method furtherincludes defining the step cycle-specific characteristic maximumacceleration values a_(max) as maxima for each step cycle ofanalogically filtered acceleration sensor signals a_(in), and the stepcycle-specific characteristic minimum acceleration values a_(min) asminima for each step cycle of the analogically filtered accelerationsensor signals a_(in).

According to another embodiment of the invention, the method furtherincludes defining the step cycle-specific characteristic maximumacceleration values a_(max) as maxima for each step cycle of digitallyfiltered acceleration sensor signals a_(in), and the step cycle-specificcharacteristic minimum acceleration values a_(min) as minima for eachstep cycle of the digitally filtered acceleration sensor signals a_(in).

According to another embodiment of the invention, the method furtherincludes defining the step cycle-specific characteristic maximumacceleration values a_(max) as mean values for each step cycle ofdigitally filtered acceleration sensor signals a_(in) over timesselected during the positive half-cycle, and the step cycle-specificcharacteristic minimum acceleration values a_(min) as mean values foreach step cycle of the digitally filtered acceleration sensor signalsa_(in) over times selected during the negative half-cycle.

According to another embodiment of the invention, the determining stepincludes using a function for the digital filtering, wherein thefunction is:

a _(out) =a _(in)/√{square root over ([1+(f/f₀)²])},

where f is the frequency and f₀ is a suitably selected boundaryfrequency.

According to another embodiment of the invention, the method furtherincludes defining step cycle-specific characteristic maximumacceleration values a_(max) as maxima for each step cycle of signalsa_(in) from the acceleration sensor filtered with digital weighting. Themethod further includes defining step cycle-specific characteristicminimum acceleration values a_(min) as minima for each step cycle of thesignals a_(in) from the acceleration sensor filtered with digitalweighting.

According to another embodiment of the invention, the method furtherincludes defining step cycle-specific characteristic maximumacceleration values a_(max) as mean values for each step cycle ofsignals a_(in) from the acceleration sensor filtered with digitalweighting over times selected during a positive half-cycle. The methodfurther includes defining step cycle-specific characteristic minimumacceleration values a_(min) as mean values for each step cycle of thesignals a_(in) from the acceleration sensor filtered with digitalweighting over times selected during a negative half-cycle.

According to another embodiment of the invention, a function used in thedigital weighted filtering is:

a _(out)(n)=(1−k)*a _(out)(n−1)+a _(in) *k,

where n indicates the n:th sample and k is the weighting factor.

According to another embodiment of the invention, the calculating stepincludes calculating the speed v based on step cycle-specificcharacteristic maximum acceleration values a_(max) of the verticalacceleration as follows:

${v \approx {k \cdot \left( {\frac{\frac{a_{\max}}{1g} + 1}{T_{step}} - f_{ref}} \right)}},$

where g is an acceleration caused by gravitation, f_(ref) is a referencefrequency and a step cycle-specific characteristic maximum accelerationvalue a_(max) is a maximum value of the vertical acceleration filteredat a suitably selected boundary frequency f₀.

According to another embodiment of the invention, the calculating stepincludes calculating comprises calculating the speed v based on stepcycle-specific characteristic minimum acceleration values a_(min) of thevertical acceleration as follows:

v≈k·√{square root over (|a _(min)|)}.

According to another embodiment of the invention, the calculating stepincludes obtaining a time T_(step) used up for one step as a timeinterval between two equivalent points, such as a maximum, a minimum, ora point of exceeding or falling below a certain value, on anacceleration graph derived from the measured values of the verticalacceleration.

According to another embodiment of the invention, the method furtherincludes calculating the step length s_(step) using the formula:

s _(step) =v*T _(step).

According to another embodiment of the invention, the method furtherincludes calculating the step rate f_(step) using the formula:

f _(step)=1/T _(step).

According to another embodiment of the invention, the method furtherincludes calculating the step count n based on a number n of equivalentpoints, such as a maximum, a minimum, or a point of exceeding or fallingbelow a certain value, on the acceleration graph given by the measuredvalues of vertical acceleration.

According to another embodiment of the invention, the method furtherincludes calculating the distance covered s as a sum of the lengths ofthe steps:

$s = {\sum\limits_{i = 1}^{n}{{s_{step}(i)}.}}$

According to another embodiment of the invention, the calculating stepincludes distinguishing between ways of progress selected from one ofwalking, running, and skiing, based on at least one of accelerationmaximum and minimum, step cycle-specific characteristic maximum andminimum acceleration values a_(max) and a_(min), and the step rate.

According to another embodiment of the invention, the calculating stepincludes making an individual calibration for each way of progressselected from one of running, walking, pole walking, or cross-countryskiing.

According to another embodiment of the invention, the method is adaptedfor use in step-by-step navigation.

According to another embodiment of the invention, there is provided adevice for measuring the progress of a moving person. The device isconfigured to measure a minimum acceleration and time such, that atleast one of the following quantities describing the progress of themoving person: speed, step rate, step count, step length, distance andway of locomotion, is calculated based on values of a verticalacceleration of a body of the moving person measured by an accelerationsensor over a measured time.

According to another embodiment of the invention, the device is furtherconfigured to determine step cycle-specific characteristic maximumacceleration values a_(max) falling within a positive half-cycle, duringan acceleration stage, and correspondingly step cycle-specificcharacteristic minimum acceleration values a_(min) falling within anegative half-cycle during a braking stage, based on measured values ofthe vertical acceleration of the body of the moving person.

According to another embodiment of the invention, the device is furtherconfigured to determine the step cycle-specific characteristic maximumacceleration values a_(max) as maxima of step cycle-specific measuredacceleration values, and the step cycle-specific characteristic minimumacceleration values a_(min) as minima of the step cycle-specificmeasured acceleration values.

According to another embodiment of the invention, the device is furtherconfigured to determine the step cycle-specific characteristic maximumacceleration values a_(max) as maxima for each step cycle ofanalogically filtered acceleration sensor signals a_(in), and the stepcycle-specific characteristic minimum acceleration values a_(min) asminima for each step cycle of the analogically filtered accelerationsensor signals a_(in).

According to another embodiment of the invention, the device is furtherconfigured to determine the step cycle-specific characteristic maximumacceleration values a_(max) as maxima for each step cycle of digitallyfiltered acceleration sensor signals a_(in), and the step cycle-specificcharacteristic minimum acceleration values a_(min) as minima for eachstep cycle of the digitally filtered acceleration sensor signals a_(in).

According to another embodiment of the invention, the device is furtherconfigured to determine the step cycle-specific characteristic maximumacceleration values a_(max) as mean values for each step cycle ofdigitally filtered acceleration sensor signals a_(in) over timesselected during the positive half-cycle. The device is furtherconfigured to determine the step cycle-specific characteristic minimumacceleration values a_(min) as mean values for each step cycle of thedigitally filtered acceleration sensor signals a_(in) over timesselected during the negative half-cycle.

According to another embodiment of the invention, the device is furtherconfigured to use, in the digital filtering, the function:

a _(out) =a _(in)/√{square root over ([1+(f/f ₀)²])},

where f is the frequency and f₀ is a suitably selected boundaryfrequency.

According to another embodiment of the invention, the device is furtherconfigured to determine step cycle-specific characteristic maximumacceleration values a_(max) as mean values for each step cycle ofsignals a_(in) from the acceleration sensor filtered with digitalweighting over times selected during a positive half-cycle. The deviceis further configured to determine step cycle-specific characteristicminimum acceleration values a_(min) as mean values for each step cycleof the signals a_(in) from the acceleration sensor filtered with digitalweighting over times selected during a negative half-cycle.

According to another embodiment of the invention, the device is furtherconfigured to determine step cycle-specific characteristic maximumacceleration values a_(max) as mean values for each step cycle ofsignals a_(in) from the acceleration sensor filtered with digitalweighting over times selected during a positive half-cycle. The deviceis further configured to determine step cycle-specific characteristicminimum acceleration values a_(min) as mean values for each step cycleof the signals a_(in) from the acceleration sensor filtered with digitalweighting over times selected during a negative half-cycle.

According to another embodiment of the invention, the device is furtherconfigured to use, in the digital weighted filtering, the function:

a _(out)(n)=(1−k)*a _(out)(n−1)+a _(in) *k,

where n indicates the n:th sample and k is the weighting factor.

According to another embodiment of the invention, the device is furtherconfigured calculate the speed v based on step cycle-specificcharacteristic maximum acceleration values a_(max) of the verticalacceleration as follows:

${v \approx {k \cdot \left( {\frac{\frac{a_{\max}}{1g} + 1}{T_{step}} - f_{ref}} \right)}},$

where g is an acceleration caused by gravitation, f_(ref) is a referencefrequency and a step cycle-specific characteristic maximum accelerationvalue a_(max) is a maximum value of the vertical acceleration filteredat a suitably selected boundary frequency f₀.

According to another embodiment of the invention, the device is furtherconfigured calculate the speed v based on step cycle-specificcharacteristic minimum acceleration values a_(min) of the verticalacceleration as follows:

v≈k·√{square root over (|a _(min)|)}.

According to another embodiment of the invention, the device is furtherconfigured, in calculating the quantities describing the progress of themoving person, to determine the time T_(step) used up for one step as atime interval between two equivalent points, such as a maximum, aminimum, or a point of exceeding or falling below a certain value, on anacceleration graph derived from the measured values of the verticalacceleration.

According to another embodiment of the invention, the device is furtherconfigured to calculate the step length s_(step) using the formula:

s _(step) =v*T _(step).

According to another embodiment of the invention, the device is furtherconfigured to calculate the step rate f_(step) using the formula:

f _(step)=1/T _(step).

According to another embodiment of the invention, the device is furtherconfigured to calculate the step count n based on a number n ofequivalent points, such as a maximum, a minimum, or a point of exceedingor falling below a certain value, on the acceleration graph given by themeasured values of vertical acceleration.

According to another embodiment of the invention, the device is furtherconfigured to calculate the distance covered s as a sum of the steplengths:

$s = {\sum\limits_{i = 1}^{n}{{s_{step}(i)}.}}$

According to another embodiment of the invention, the device is furtherconfigured to distinguish between ways of progress selected from one ofwalking, running, and skiing, based on at least one of accelerationmaximum and minimum, step cycle-specific characteristic maximum andminimum acceleration values a_(max) and a_(min), and the step rate.

According to another embodiment of the invention, the device is furtherconfigured to make an individual calibration for each way of progressselected from one of running, walking, pole walking, or cross-countryskiing.

According to another embodiment of the invention, the device is furtherconfigured for use in step-by-step navigation.

According to another embodiment of the invention, the device is furtherconfigured to cooperate with at least one of an altimeter, satellitenavigation devices, and a magnetometer.

According to another embodiment of the invention, the device is furtherconfigured to receive and utilize at least one of map database data andterrain inclination data.

According to another embodiment of the invention, there is provided adevice configured to be positioned at a middle of a body of a movingperson, the device is configured to measure a minimum acceleration andtime such, that at least one of the following quantities describing theprogress of the moving person: speed, step rate, step count, steplength, distance and way of locomotion, is calculated based on values ofa vertical acceleration of a body of the moving person measured by anacceleration sensor over a measured time.

According to another embodiment of the invention, the device is furtherconfigured to be positioned at the middle of the body of the movingperson can be configured to a piece of clothing, a piece of headwear,the neck, a pocket, or a belt of the moving person.

According to another embodiment of the invention, there is provided adisplay unit for a moving person, wherein the display unit for themoving person is configured to cooperate with a device. The device isconfigured to measure a minimum acceleration and time such, that atleast one of the following quantities describing the progress of themoving person: speed, step rate, step count, step length, distance andway of locomotion, is calculated based on values of a verticalacceleration of a body of the moving person measured by an accelerationsensor over a measured time.

According to another embodiment of the invention, there is provided asystem for measuring a progress of a moving person. The system includesa device configured to measure a minimum acceleration and time such,that at least one of the following quantities describing the progress ofthe moving person: speed, step rate, step count, step length, distanceand way of locomotion, is calculated based on values of a verticalacceleration of a body of the moving person measured by an accelerationsensor over a measured time. The system further includes a display unitfor the moving person that is configured to cooperate with the device.

According to another embodiment of the invention, the device formeasuring the progress of the moving person and the display unit for themoving person are integrated in one device.

BRIEF DESCRIPTION OF DRAWINGS

Below, the invention and its preferred embodiments are described indetail with exemplary reference to the enclosed figures, of which:

FIG. 1 shows a diagram of a measuring apparatus according to theinvention,

FIG. 2 shows a view of a measuring unit according to the invention, and

FIG. 3 shows a view of an alternative measuring unit according to theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a diagram of a measuring apparatus according to theinvention. The apparatus can consist of a measuring unit 1, a storageunit 2 and a display unit 3. These communicate with each other usingwireless or wired connections. Some of the units, or all of them, can beintegrated in the same casing or unit. The measuring unit is attachedclose to the human body, e.g. close to the middle. The measuring unit istypically positioned at some garment of the moving person, like e.g. apiece of clothing, a piece of headwear, the neck, a pocket, or close tothe middle, i.e. close to the body's center of gravity, e.g. at thebelt. The display unit is typically located in a clearly visibleposition. It can be integrated, for example, in a measuring and storageunit, or it can be separate. It can also be part of a watch, a satellitenavigator, a mobile terminal, a radio receiver, a player, or the like.Any calibration data for the measuring device are stored in one unit orin several units.

FIG. 2 shows a view of a measuring unit according to the invention. Themeasuring unit 1 can comprise an acceleration sensor 4 of 1 to 3 axes, aunit 5 for analysis and diagnostics of the acceleration data, a volatileand a nonvolatile memory 6, a communication unit 7, and a power supply8, e.g. a battery, an accumulator, a harvester or some similar device.The analysis unit can, for example, be based on a microprocessor or aDSP (Digital Signal Processor). The memory stores, for instance, userdata, calibration data, measurement data and other log data. Thecommunication unit comprises, for example, a transfer protocolgenerator, a required interface, or a radio transmitter, a receiver andan antenna.

The measuring unit can be positioned fastened close to the human body,like, for example, close to the middle, i.e. close to the body's centerof gravity. The measuring unit is, typically, positioned at the clothingof the moving person, like, for instance, a piece of clothing, a pieceof headwear, the neck, a pocket, or the belt.

FIG. 3 shows a view of an alternative measuring unit according to theinvention. If, in addition to the speed and the distance covered, onewants to know the traveled route, a magnetometer 11 of 2 or 3 axes canbe added to the alternative measuring unit for the compass direction tobe determined for each step, or once in a while.

In the solution according to the invention, the acceleration of thecyclic motion of progress is being measured in one or more directions.From the vertical acceleration values measured during each step cycle, acharacteristic maximum acceleration a_(max) occurring during thepositive half cycle or the acceleration stage and, respectively, acharacteristic minimum acceleration a_(min) occurring during thenegative half cycle or the braking stage are being determined.

As values of the characteristic maximum acceleration a_(max) and thecharacteristic minimum acceleration a_(min) accelerations are defined,that clearly differ from zero, whereby the influence of the zero pointerror in the acceleration sensor or of the coupling of gravitation,caused by inclination, on the metering signal is minimal, since they areclearly lower than the values a_(max) and a_(min).

In the solution according to the invention, the characteristic maximumacceleration a_(max) and the characteristic minimum acceleration a_(min)can be defined, for example, directly as the maximum and/or the minimumof the vertical acceleration value from the raw data measured by theacceleration sensor. Alternatively, in the solution according to theinvention, the values a_(max) and a_(min) can be defined by filteringthe acceleration sensor signal a_(in) analogically by, for example,mechanical damping of the signal a_(in).

Further, alternatively, in a solution according to the invention, thevalues a_(max) and a_(min) can be defined by filtering the accelerationsensor signal a_(in) digitally, by means of, for example, an RC filter.In this case, in the digital filtering, the function used in the firststage filtering could be, for instance:

a _(out) =a _(in)/√{square root over ([1+(f/f ₀)²])},

where f=frequency and f₀=the boundary frequency for −3 dB and the valuesa_(max) and a_(min) can be defined based on this filtered signal as, forexample, the maximum and/or the minimum of the filtered accelerationvalue.

Further, alternatively, in the solution according to the invention, thevalues a_(max) and a_(min) can be defined by filtering the accelerationsensor signal a_(in) by means of digital weighting. Here, the functionto be used in the digital weighting could be, for instance:

a _(out)(n)=(1−k)*a _(out)(n−1)+a _(in) *k,

where n indicates the n:th sample and k is the weighting factor.

Further, alternatively, in a solution according to the invention, thevalues a_(max) and a_(min) can be defined by using a mean valuecalculated from the measured acceleration value over times selectedduring the positive and/or the negative half cycle.

The time used up for one step T_(step) is obtained as the time intervalbetween two equivalent points, such a maximum, a minimum, or a point ofexceeding or falling below a certain value, on the acceleration graphgiven by the measured values of vertical acceleration. The time T_(C)spent in ground contact during a step is obtained based on the length oftime of zero acceleration in the acceleration graph derived from themeasured vertical acceleration values.

For running, it has been noted that the speed is proportional to theinverse of the contact time and to the force produced in the take off.Since the average vertical acceleration of the body is zero,

T _(C) ·a _(max)+(T _(step) −T _(C))·a _(min)=0,

the speed of locomotion v is obtained based on the characteristicmaximum acceleration a_(max), in other words,

${v \approx {k \cdot \left( {\frac{\frac{a_{\max}}{1g} + 1}{T_{step}} - f_{ref}} \right)}},$

where g is the acceleration caused by gravitation, f_(ref) is areference frequency and the characteristic maximum acceleration a_(max)is the maximum value of the vertical acceleration strongly filtered at,for instance, the boundary frequency f₀=6 Hz. In running, thecharacteristic maximum acceleration a_(max) of the middle or some otherpart of the body is a good measure of the speed of progress.

For walking, the speed is obtained based on the characteristic minimumacceleration a_(min) of the vertical acceleration, in other words,

v≈k·√{square root over (|a _(min)|)}.

The factors k depend, to some extent, on the boundary frequency in thefiltering of the acceleration data. In walking, the characteristicminimum acceleration a_(min) of the middle or some other part of thebody is a good measure of the speed of progress.

In the solution according to the invention, the step length s_(step) canbe calculated using the formula:

s _(step) =v*T _(step),

and, correspondingly, the step rate or the cadence f_(step) can becalculated using the formula:

f _(step)=1/T _(step).

In the solution according to the invention, running and walking can bedistinguished from each other based on step rate and speed of progress.At low running speeds, a non-linear model can be used, and running andwalking can be adapted to each other.

In the solution according to the invention, the step count n can becalculated on the basis of the number n of equivalent points, such amaximum, a minimum, or a point of exceeding or falling below a certainvalue, on the acceleration graph given by the measured values ofvertical acceleration. Further, in the solution according to theinvention, the distance covered s can be calculated as the sum of thestep lengths:

$s = {\sum\limits_{i = 1}^{n}{{s_{step}(i)}.}}$

In the solution according to the invention, a single acceleration sensorof one axis can be used, and thus, implementing the calculations of theformulae presented above is a simple task by means of, for example, amicrocontroller. This enables a small, low cost, and low power sensorsolution, by means of which a precision sufficient for consumer productsis achieved. Without individual calibration, the relative error, atdistances exceeding one kilometer, is less than 10%.

In the solution according to the invention, an acceleration sensor ofmany axes can be used as well, and that enables, for example, diagnosingstationary running.

In the solution according to the invention, a magnetometer of two axescan also be used, by means of which the length and direction of everystep can be obtained. There will be inclination compensation as well,since the inclination of the body is more or less constant. Calibrationof direction and speed can be done by running a straight line back andforth.

In the solution according to the invention, the speed estimate suffers aminimal impact from the zero point error in the acceleration sensor orfrom gravitation coupling into the metering signal caused byinclination, when using the characteristic maximum acceleration a_(max)and the characteristic minimum acceleration a_(min), which values arelarge numbers in comparison with those. The ways of progress, e.g.walking, running, and skiing, can be distinguished from each other basedon the characteristic maximum acceleration a_(max), the characteristicminimum acceleration a_(min), and/or the step rate.

In the solution according to the invention, based on the accelerationvalues measured during the step cycles, characteristic maximumacceleration and characteristic minimum acceleration values a_(max) anda_(min) for each step cycle are defined, by means of which values thespeed, the step rate, the step length, and the distance can becalculated with low power consumption using simple arithmetic, forexample by using a polynome.

The system, even if not calibrated, provides good precision. In order toimprove precision, individual calibration can be made for differentmodes of progress, e.g. running, walking, pole walking, or cross-countryskiing. This can be done over a known distance using one speed or amultitude of speeds. By repeating the calibration, errors in speed anddistance caused by stochastic errors are reduced, whereby precision isfurther improved. New calibration data can be added to the old data bysuitable digital filtering. In addition, for further improvement of theprecision, information about the characteristic maximum and minimumacceleration values a_(max) and a_(min) can be combined with contacttime data, with change in altitude and terrain inclination data obtainedfrom an altimeter, and/or with satellite navigation.

A complete step-by-step navigation unit is provided by adding to thestep data the compass direction obtained from a magnetometer. Themagnetometer can be calibrated, e.g. by rotating about a vertical axis.A direction error in the installation can be calibrated away by, e.g.walking a selected calibration route back and forth. Absolute coordinatedata is obtained by combining this navigation unit with satellitenavigation. Precision is further improved by combining the navigationunit with a map database and with an altimeter, since plausibilitychecks of the coordinates and movement can be made based on the altitudeand changes in altitude.

By using an acceleration sensor signal perpendicular to the principalmetering direction, a measure of the efficiency of locomotion isobtained.

In the solution according to the invention, characteristic maximumacceleration and characteristic minimum acceleration values a_(max) anda_(min) and/or maximum and/or minimum acceleration values obtained froman acceleration sensor of one or more axes can be used for estimatingthe speed of progress of a person. The signal of the acceleration sensorcan be suitably filtered by means of mechanical, electronic, analogand/or digital filtering such, that the speed estimate is as exact andreliable as possible. In the solution according to the invention, steptime, step rate, step length, and distance accumulated from the stepscan be calculated based on the speed and the time interval betweenconsecutive maxima or minima.

In the solution according to the invention, walking, running, andskiing, or some other way of progress can be distinguished from eachother based on, for example, the maximum and minimum acceleration of themiddle of the body, the characteristic maximum and minimum accelerationvalues a_(max) and a_(min) and/or the step rate.

In the solution according to the invention, the parameters for anaverage person running and walking can be utilized without individualcalibration of the measuring system. The measuring system can becalibrated by means of individual calibration for one speed or for amultitude of speeds for a certain way of progress, e.g. running orwalking. In the solution according to the invention, the calibration ofthe measuring system can be repeated such, that new data is combinedwith the old data by digital filtering. The precision of the measuringsystem can be improved by combining contact time data with the maximumand minimum acceleration data.

In the solution according to the invention, the direction of each stepor the direction of the distance covered observed from time to time canbe determined by combining the speed estimate with the compass directionobtained from a magnetometer of 2 or 3 axes. A magnetometer and aninstallation direction error can be compensated for by rotating about avertical axis and by walking a selected calibration route back andforth.

In the solution according to the invention, the efficiency of thelocomotion can be estimated by combining with the characteristic maximumacceleration values and the characteristic minimum acceleration valuesa_(max) and a_(min) and/or with the maximum and minimum accelerationvalue data, acceleration values measured at right angles to those.

By means of the method and device according to the invention, aprecision is achieved equal to that of the best methods presented above,by an implementation solution of significantly greater simplicity,utilizing one acceleration sensor without inclination compensation.

By means of the method and device according to the invention, thecomplicated algorithms of prior systems are avoided, and low cost, lowpower consumption, and small size are achieved.

The low power consumption of the method and device according to theinvention allows a small battery and gives it long life, or even abattery-free solution based on, for example, recovery of the kineticenergy occurring in the measuring device (harvesting).

The simple measuring algorithm of the method and device according to theinvention allows the computations to be performed entirely in themeasuring unit, which reduces the need for data transfer from themeasuring unit, and thus, the power consumption of data transmissionutilizing radio traffic.

The small size of the measuring unit of the solution according to theinvention allows the unit to be positioned, for example, at a piece ofgarment of the moving person, like, for example a piece of clothing, apiece of headwear, the neck, a pocket or close to the middle of thebody, i.e. near the center of gravity of the body, at the belt, forinstance. The method according to the invention is applicable, forexample, to both slow and fast running, to walking at various speeds,pole walking, cross-country skiing, downhill sports, roller skiing,roller-skating and skating.

The method and device according to the invention can be used formeasuring a moving person's speed, the step length, and the distancecovered, based on maximum and minimum acceleration values of the body,given by an acceleration sensor of one axis for vertical accelerationand/or characteristic maximum and minimum acceleration values a_(max)and a_(min). In the solution according to the invention, theacceleration signal can be optimally filtered such, that theacceleration signal gives as good a picture of the speed as possible.

In the solution according to the invention, the ways of locomotion ofthe moving person, like walking and running, can be distinguished fromeach other based on the cadence and the speed of locomotion. In thesolution according to the invention the parameters for an average personwalking and running can be utilized without any individual calibrationof the measuring system. The solution according to the invention enablescalibration of the single point measuring system for walking and forrunning.

The solution according to the invention enables diagnosing stationaryrunning by means of a sensor of longitudinal acceleration. The solutionaccording to the invention enables the direction of each step and thedistance covered to be determined by means of a compass of two or threeaxes. The solution according to the invention enables calibration of theinstallation error of the compass by traveling the same route back andforth.

1. A method for measuring the progress of a moving person, the methodcomprising: calculating at least one of the following quantitiesdescribing the progress of the moving person: speed, step rate, stepcount, step length, distance and way of progress, based on values of avertical acceleration of a body of the moving person measured by anacceleration sensor over a measured time.
 2. The method according toclaim 1, further comprising: defining step cycle-specific characteristicmaximum acceleration values a_(max) falling within a positivehalf-cycle, during an acceleration stage, and correspondingly stepcycle-specific characteristic minimum acceleration values a_(min)falling within a negative half-cycle during a braking stage, based onmeasured values of the vertical acceleration of the body of the movingperson.
 3. The method according to claim 2, further comprising: definingthe step cycle-specific characteristic maximum acceleration valuesa_(max) as maxima of step cycle-specific measured acceleration values,and the step cycle-specific characteristic minimum acceleration valuesa_(min) as minima of the step cycle-specific measured accelerationvalues.
 4. The method according to claim 2, further comprising: definingthe step cycle-specific characteristic maximum acceleration valuesa_(max) as maxima for each step cycle of analogically filteredacceleration sensor signals a_(in), and the step cycle-specificcharacteristic minimum acceleration values a_(min) as minima for eachstep cycle of the analogically filtered acceleration sensor signalsa_(in).
 5. The method according to claim 2, further comprising: definingthe step cycle-specific characteristic maximum acceleration valuesa_(max) as maxima for each step cycle of digitally filtered accelerationsensor signals a_(in), and the step cycle-specific characteristicminimum acceleration values a_(min) as minima for each step cycle of thedigitally filtered acceleration sensor signals a_(in).
 6. The methodaccording to claim 2, further comprising: defining the stepcycle-specific characteristic maximum acceleration values a_(max) asmean values for each step cycle of digitally filtered accelerationsensor signals a_(in) over times selected during the positivehalf-cycle, and the step cycle-specific characteristic minimumacceleration values a_(min) as mean values for each step cycle of thedigitally filtered acceleration sensor signals a_(in) over timesselected during the negative half-cycle.
 7. The method according toclaim 1, wherein the determining comprises using a function for thedigital filtering, wherein the function is:a _(out) =a _(in)/√{square root over ([1+(f/f ₀)²])}, where f is thefrequency and f₀ is a suitably selected boundary frequency.
 8. Themethod according to claim 1, further comprising: defining stepcycle-specific characteristic maximum acceleration values a_(max) asmaxima for each step cycle of signals a_(in) from the accelerationsensor filtered with digital weighting; and defining step cycle-specificcharacteristic minimum acceleration values a_(min) as minima for eachstep cycle of the signals a_(in) from the acceleration sensor filteredwith digital weighting.
 9. The method according to claim 1, furthercomprising: defining step cycle-specific characteristic maximumacceleration values a_(max) as mean values for each step cycle ofsignals a_(in) from the acceleration sensor filtered with digitalweighting over times selected during a positive half-cycle; and definingstep cycle-specific characteristic minimum acceleration values a_(min)as mean values for each step cycle of the signals a_(in) from theacceleration sensor filtered with digital weighting over times selectedduring a negative half-cycle.
 10. The method according to claim 8,wherein a function used in the digital weighted filtering is:a _(out)(n)=(1−k)*a _(out)(n−1)+a _(in) *k, where n indicates the n:thsample and k is the weighting factor.
 11. The method according to claim1, wherein the calculating comprises calculating the speed v based onstep cycle-specific characteristic maximum acceleration values a_(max)of the vertical acceleration as follows:${v \approx {k \cdot \left( {\frac{\frac{a_{\max}}{1g} + 1}{T_{step}} - f_{ref}} \right)}},$where g is an acceleration caused by gravitation, f_(ref) is a referencefrequency and a step cycle-specific characteristic maximum accelerationvalue a_(max) is a maximum value of the vertical acceleration filteredat a suitably selected boundary frequency f₀.
 12. The method accordingto claim 1, wherein the calculating comprises calculating the speed vbased on step cycle-specific characteristic minimum acceleration valuesa_(min) of the vertical acceleration as follows:v≈k·√{square root over (|a _(min)|)}.
 13. The method according to claim1, wherein the calculating comprises obtaining a time T_(step) used upfor one step as a time interval between two equivalent points, such as amaximum, a minimum, or a point of exceeding or falling below a certainvalue, on an acceleration graph derived from the measured values of thevertical acceleration.
 14. The method according to claim 13, furthercomprising: calculating the step length s_(step) using the formula:s _(step) =v*T _(step).
 15. The method according to claim 13, furthercomprising: calculating the step rate f_(step) using the formula:f _(step)=1/T _(step).
 16. The method according to claim 13, furthercomprising: calculating the step count n based on a number n ofequivalent points, such as a maximum, a minimum, or a point of exceedingor falling below a certain value, on the acceleration graph given by themeasured values of vertical acceleration.
 17. The method according toclaim 13, further comprising: calculating the distance covered s as asum of the lengths of the steps:$s = {\sum\limits_{i = 1}^{n}{{s_{step}(i)}.}}$
 18. The methodaccording to claim 1, wherein the calculating comprises distinguishingbetween ways of progress selected from one of walking, running, andskiing, based on at least one of acceleration maximum and minimum, stepcycle-specific characteristic maximum and minimum acceleration valuesa_(max) and a_(min), and the step rate.
 19. The method according toclaim 18, wherein the calculating comprises making an individualcalibration for each way of progress selected from one of running,walking, pole walking, or cross-country skiing.
 20. The method accordingto claim 1, wherein the method is adapted for use in step-by-stepnavigation.
 21. A device for measuring the progress of a moving person,the device being configured measure a minimum acceleration and timesuch, that at least one of the following quantities describing theprogress of the moving person: speed, step rate, step count, steplength, distance and way of locomotion, is calculated based on values ofa vertical acceleration of a body of the moving person measured by anacceleration sensor over a measured time.
 22. The device according toclaim 21, wherein the device is further configured to determine stepcycle-specific characteristic maximum acceleration values a_(max)falling within a positive half-cycle, during an acceleration stage, andcorrespondingly step cycle-specific characteristic minimum accelerationvalues a_(min) falling within a negative half-cycle during a brakingstage, based on measured values of the vertical acceleration of the bodyof the moving person.
 23. The device according to claim 22, wherein thedevice is further configured to determine the step cycle-specificcharacteristic maximum acceleration values a_(max) as maxima of stepcycle-specific measured acceleration values, and the step cycle-specificcharacteristic minimum acceleration values a_(min) as minima of the stepcycle-specific measured acceleration values.
 24. The device according toclaim 22, wherein the device is further configured to determine the stepcycle-specific characteristic maximum acceleration values a_(max) asmaxima for each step cycle of analogically filtered acceleration sensorsignals a_(in), and the step cycle-specific characteristic minimumacceleration values a_(min) as minima for each step cycle of theanalogically filtered acceleration sensor signals a_(in).
 25. The deviceaccording to claim 22, wherein the device is further configured todetermine the step cycle-specific characteristic maximum accelerationvalues a_(max) as maxima for each step cycle of digitally filteredacceleration sensor signals a_(in), and the step cycle-specificcharacteristic minimum acceleration values a_(min) as minima for eachstep cycle of the digitally filtered acceleration sensor signals a_(in).26. The device according to claim 22, wherein the device is furtherconfigured to determine the step cycle-specific characteristic maximumacceleration values a_(max) as mean values for each step cycle ofdigitally filtered acceleration sensor signals a_(in) over timesselected during the positive half-cycle, and the step cycle-specificcharacteristic minimum acceleration values a_(min) as mean values foreach step cycle of the digitally filtered acceleration sensor signalsa_(in) over times selected during the negative half-cycle.
 27. Thedevice according to claim 21, wherein the device is configured to use,in the digital filtering, the function:a _(out) =a _(in)/√{square root over ([1+(f/f ₀)²])}, where f is thefrequency and f₀ is a suitably selected boundary frequency.
 28. Thedevice according to claim 21, wherein the device is configured todetermine step cycle-specific characteristic maximum acceleration valuesa_(max) as mean values for each step cycle of signals a_(in) from theacceleration sensor filtered with digital weighting over times selectedduring a positive half-cycle; and determine step cycle-specificcharacteristic minimum acceleration values a_(min) as mean values foreach step cycle of the signals a_(in) from the acceleration sensorfiltered with digital weighting over times selected during a negativehalf-cycle.
 29. The device according to claim 21, wherein the device isconfigured to determine step cycle-specific characteristic maximumacceleration values a_(max) as mean values for each step cycle ofsignals a_(in) from the acceleration sensor filtered with digitalweighting over times selected during a positive half-cycle; anddetermine step cycle-specific characteristic minimum acceleration valuesa_(min) as mean values for each step cycle of the signals a_(in) fromthe acceleration sensor filtered with digital weighting over timesselected during a negative half-cycle.
 30. The device according to claim28, wherein the device is configured to use, in the digital weightedfiltering, the function:a _(out)(n)=(1−k)*a _(out)(n−1)+a _(in) *k, where n indicates the n:thsample and k is the weighting factor.
 31. The device according to claim21, wherein the device is configured to calculate the speed v based onstep cycle-specific characteristic maximum acceleration values a_(max)of the vertical acceleration as follows:${v \approx {k \cdot \left( {\frac{\frac{a_{\max}}{1g} + 1}{T_{step}} - f_{ref}} \right)}},$where g is an acceleration caused by gravitation, f_(ref) is a referencefrequency and a step cycle-specific characteristic maximum accelerationvalue a_(max) is a maximum value of the vertical acceleration filteredat a suitably selected boundary frequency f₀.
 32. The device accordingto claim 21, wherein the device is configured to calculate the speed vbased on step cycle-specific characteristic minimum acceleration valuesa_(min) of the vertical acceleration as follows:v≈k·√{square root over (|a _(min)|)}.
 33. The device according to claim21, wherein the device is configured, in calculating the quantitiesdescribing the progress of the moving person, to determine the timeT_(step) used up for one step as a time interval between two equivalentpoints, such as a maximum, a minimum, or a point of exceeding or fallingbelow a certain value, on an acceleration graph derived from themeasured values of the vertical acceleration.
 34. The device accordingto claim 33, wherein the device is configured to calculate the steplength s_(step) using the formula:s _(step) =v*T _(step).
 35. The device according to claim 33, whereinthe device is configured to calculate the step rate f_(step) using theformula:f _(step)=1/T _(step).
 36. The device according to claim 33, wherein thedevice is configured to calculate the step count n based on a number nof equivalent points, such as a maximum, a minimum, or a point ofexceeding or falling below a certain value, on the acceleration graphgiven by the measured values of vertical acceleration.
 37. The deviceaccording to claim 33, wherein the device is configured to calculate thedistance covered s as a sum of the step lengths:$s = {\sum\limits_{i = 1}^{n}{{s_{step}(i)}.}}$
 38. The deviceaccording to claim 21, wherein the device is configured to distinguishbetween ways of progress selected from one of walking, running, andskiing, based on at least one of acceleration maximum and minimum, stepcycle-specific characteristic maximum and minimum acceleration valuesa_(max) and a_(min), and the step rate.
 39. The device according toclaim 38, wherein the device is configured to make an individualcalibration for each way of progress selected from one of running,walking, pole walking, or cross-country skiing.
 40. The device accordingto claim 21, wherein the device is configured for use in step-by-stepnavigation.
 41. The device according to claim 40, wherein the device isconfigured to cooperate with at least one of an altimeter, satellitenavigation devices, and a magnetometer.
 42. The device according toclaim 40, wherein the device is configured to receive and utilize atleast one of map database data and terrain inclination data.
 43. Adevice configured to be positioned at a middle of a body of a movingperson, wherein the device comprises a device according to claim 21 formeasuring the progress of the moving person.
 44. The device according toclaim 43, wherein the device configured to be positioned at the middleof the body of the moving person can be configured to a piece ofclothing, a piece of headwear, the neck, a pocket, or a belt of themoving person.
 45. A display unit for a moving person, wherein thedisplay unit for the moving person is configured to cooperate with adevice according to claim 21 measuring the progress of a moving person.46. A system for measuring a progress of a moving person, wherein thesystem comprises a device according to claim 21 for measuring theprogress of the moving person, and a display unit for the moving personthat is configured to cooperate with the device.
 47. The systemaccording to claim 46, wherein the device for measuring the progress ofthe moving person and the display unit for the moving person areintegrated in one device.